<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Klasses and objects.: XML Security Library Reference Manual</title>
<meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
<link rel="home" href="index.html" title="XML Security Library Reference Manual">
<link rel="up" href="xmlsec-notes-new-crypto.html" title="Adding support for new cryptographic library.">
<link rel="prev" href="xmlsec-notes-new-crypto-functions.html" title="xmlSecCryptoApp* functions.">
<link rel="next" href="xmlsec-notes-new-crypto-transforms.html" title="Cryptographic transforms.">
<meta name="generator" content="GTK-Doc V1.27 (XML mode)">
<link rel="stylesheet" href="style.css" type="text/css">
<style type="text/css">
table.CALSTABLE > tbody > tr:nth-child(1) > td:nth-child(1) {
    width: 20em;
}
.synopsis, .classsynopsis {
    background: #eeeeee;
    border: solid 1px #aaaaaa;
}
.programlisting {
    background: #eeeeee;
    border: solid 1px #000000;
}
.navigation {
    background: #eeeeee;
    border: solid 1px #000000;
}
.navigation a {
    color: initial;
}
.navigation a:visited {
    color: initial;
}
</style>
<style type="text/css">
table.CALSTABLE > tbody > tr:nth-child(1) > td:nth-child(1) {
    width: 20em;
}
.synopsis, .classsynopsis {
    background: #eeeeee;
    border: solid 1px #aaaaaa;
}
.programlisting {
    background: #eeeeee;
    border: solid 1px #000000;
}
.navigation {
    background: #eeeeee;
    border: solid 1px #000000;
}
.navigation a {
    color: initial;
}
.navigation a:visited {
    color: initial;
}
</style>
</head>
<body><table width="100%" valign="top"><tr valign="top">
<td valign="top" align="left" width="210">
<img src="../images/logo.gif" alt="XML Security Library" border="0"><p></p>
<ul>
<li><a href="../index.html">Home</a></li>
<li><a href="../download.html">Download</a></li>
<li><a href="../news.html">News</a></li>
<li><a href="../documentation.html">Documentation</a></li>
<ul>
<li><a href="../faq.html">FAQ</a></li>
<li><a href="../api/xmlsec-notes.html">Tutorial</a></li>
<li><a href="../api/xmlsec-reference.html">API reference</a></li>
<li><a href="../api/xmlsec-examples.html">Examples</a></li>
</ul>
<li><a href="../xmldsig.html">XML Digital Signature</a></li>
<ul><li><a href="http://www.aleksey.com/xmlsec/xmldsig-verifier.html">Online Verifier</a></li></ul>
<li><a href="../xmlenc.html">XML Encryption</a></li>
<li><a href="../c14n.html">XML Canonicalization</a></li>
<li><a href="../bugs.html">Reporting Bugs</a></li>
<li><a href="http://www.aleksey.com/pipermail/xmlsec">Mailing list</a></li>
<li><a href="../related.html">Related</a></li>
<li><a href="../authors.html">Authors</a></li>
</ul>
<table width="100%">
<tr>
<td width="15"></td>
<td><a href="http://xmlsoft.org/"><img src="../images/libxml2-logo.png" alt="LibXML2" border="0"></a></td>
</tr>
<tr>
<td width="15"></td>
<td><a href="http://xmlsoft.org/XSLT"><img src="../images/libxslt-logo.png" alt="LibXSLT" border="0"></a></td>
</tr>
<tr>
<td width="15"></td>
<td><a href="http://www.openssl.org/"><img src="../images/openssl-logo.png" alt="OpenSSL" border="0"></a></td>
</tr>
<!--Links - start--><!--Links - end-->
</table>
</td>
<td valign="top"><table width="100%" valign="top"><tr><td valign="top" align="left" id="xmlsecContent">
<table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="5"><tr valign="middle">
<td width="100%" align="left" class="shortcuts"></td>
<td><a accesskey="h" href="index.html"><img src="home.png" width="16" height="16" border="0" alt="Home"></a></td>
<td><a accesskey="u" href="xmlsec-notes-new-crypto.html"><img src="up.png" width="16" height="16" border="0" alt="Up"></a></td>
<td><a accesskey="p" href="xmlsec-notes-new-crypto-functions.html"><img src="left.png" width="16" height="16" border="0" alt="Prev"></a></td>
<td><a accesskey="n" href="xmlsec-notes-new-crypto-transforms.html"><img src="right.png" width="16" height="16" border="0" alt="Next"></a></td>
</tr></table>
<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="xmlsec-notes-new-crypto-klasses"></a>Klasses and objects.</h2></div></div></div>
<p>The XML Security Library is written in C but it uses some OOP techniques:
	the objects in the library have "klasses" and there is "klasses" inheritance.
	(see <a class="link" href="xmlsec-signature-klasses.html" title="APPENDIX A. XML Security Library Signature Klasses.">signature</a> and
	<a class="link" href="xmlsec-encryption-klasses.html" title="APPENDIX B. XML Security Library Encryption Klasses.">encryption</a> klasses 
	diagrams). The "klass" is different from C++ "class" (btw, this is 
	one of the reasons why it is spelled differently). The idea of "klasses" 
	used in XML Security Library are close to one in the GLIB/GTK/GNOME
	and many other C projects. If you ever seen an OOP code written in C
	you should find everything familiar.
	</p>
<p>XML Security Library "klass" includes three main parts:
	</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>"Klass" declaration structure that defines "klass" interfaces
	and global constant data (for example, the human-readable name of 
	the "klass").
	</p>
<div class="example">
<a name="id-1.2.14.5.3.1.1.1.1"></a><p class="title"><b>Example 30. Base transform "klass" and its child XPath transform "klass" structure.</b></p>
<div class="example-contents"><pre class="programlisting">
struct _xmlSecTransformKlass {
    /* data */
    size_t				klassSize;
    size_t				objSize;
    const xmlChar*			name;
    const xmlChar*			href;
    xmlSecTransformUsage		usage;

    /* methods */
    xmlSecTransformInitializeMethod	initialize;
    xmlSecTransformFinalizeMethod	finalize;

    xmlSecTransformNodeReadMethod	readNode;
    xmlSecTransformNodeWriteMethod	writeNode;

    ...
};

...

static xmlSecTransformKlass xmlSecTransformXPathKlass = {
    /* klass/object sizes */
    sizeof(xmlSecTransformKlass),	/* size_t klassSize */
    xmlSecXPathTransformSize,		/* size_t objSize */

    xmlSecNameXPath,			/* const xmlChar* name; */
    xmlSecXPathNs, 			/* const xmlChar* href; */
    xmlSecTransformUsageDSigTransform,	/* xmlSecTransformUsage	usage; */

    xmlSecTransformXPathInitialize,	/* xmlSecTransformInitializeMethod initialize; */
    xmlSecTransformXPathFinalize,	/* xmlSecTransformFinalizeMethod finalize; */
    xmlSecTransformXPathNodeRead,	/* xmlSecTransformNodeReadMethod readNode; */
    NULL,				/* xmlSecTransformNodeWriteMethod writeNode; */
    
    ...
};
	    </pre></div>
</div>
<p><br class="example-break">
	</p>
</li>
<li class="listitem">
<p>"Klass" id which is simply a pointer to the "klass"
	declaration strucutre. "Klass" id is used to bind "klass" objects 
	to the "klass" declaration and to pass "klass" strucutre to functions.
	</p>
<div class="example">
<a name="id-1.2.14.5.3.1.2.1.1"></a><p class="title"><b>Example 31. Base transform "klass" id declaration and its child XPath transform "klass" id implementation.</b></p>
<div class="example-contents"><pre class="programlisting">
typedef const struct _xmlSecTransformKlass		xmlSecTransformKlass, *xmlSecTransformId;

...

#define xmlSecTransformXPathId 		xmlSecTransformXPathGetKlass()

...

xmlSecTransformId 
xmlSecTransformXPathGetKlass(void) {
    return(&amp;xmlSecTransformXPathKlass);
}
	    </pre></div>
</div>
<p><br class="example-break">
	</p>
</li>
<li class="listitem">
<p>"Klass" object structure that contains object specific
	data. The child object specific data are placed after the parent "klass"
	object data.
	</p>
<div class="example">
<a name="id-1.2.14.5.3.1.3.1.1"></a><p class="title"><b>Example 32. Base transform object strucutre and its child XPath transform object.</b></p>
<div class="example-contents"><pre class="programlisting">
struct _xmlSecTransform {
    xmlSecTransformId 			id; 
    xmlSecTransformOperation		operation;
    xmlSecTransformStatus		status;
    xmlNodePtr				hereNode;

    /* transforms chain */
    xmlSecTransformPtr			next;
    xmlSecTransformPtr			prev;
    
    ...
};

...

/******************************************************************************
 *
 * XPath/XPointer transforms
 *
 * xmlSecPtrList with XPath expressions is located after xmlSecTransform structure
 * 
 *****************************************************************************/
#define xmlSecXPathTransformSize	\
    (sizeof(xmlSecTransform) + sizeof(xmlSecPtrList))
#define xmlSecXPathTransformGetDataList(transform) \
    ((xmlSecTransformCheckSize((transform), xmlSecXPathTransformSize)) ? \
	(xmlSecPtrListPtr)(((unsigned char*)(transform)) + sizeof(xmlSecTransform)) : \
	(xmlSecPtrListPtr)NULL)
	    </pre></div>
</div>
<p><br class="example-break">
	</p>
</li>
</ul></div>
<p>
	</p>
</div>
<div class="footer">
<hr>Generated by GTK-Doc V1.27</div>
</td></tr></table></td>
</tr></table></body>
</html>
